change modifier onlyVerified to onlyValidProof and unit tests

[mnusurov]

PR Description

This PR introduces several key updates and improvements to enhance the security and functionality of our wallet system, with a particular focus on integrating zero-knowledge (ZK) proof verification. The changes span across the wallet contract, its related tests, and the World ID interface.

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Changes

Wallet Contract (src/Wallet.sol)

• Immutable Variables:
  Changed owner and worldID to immutable for improved efficiency.
• Nullifier Hashes:
  Introduced the nullifierHashes mapping to store used nullifier hashes.
• Modifier Update:
  Replaced the onlyVerified modifier with onlyValidProof to ensure that a valid ZK proof is provided.
• Transfer Function:
  Modified the transfer function to accept a ZK proof as an additional parameter.
• Function Removal:
  Removed the createWorldId function since it was empty.
• Token Support:
  Removed the usdt state variable and added USDT as a supported token in the constructor.

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Wallet Test (test/Wallet.t.sol)

• Variable Renaming:
  Renamed worldID to mockWorldID for clarity.
• Setup Update:
  Updated the setUp function to use mockWorldID.
• Test Enhancements:
  • Updated tests to supply a valid ZK proof when calling the transfer function.
  • Added tests to verify the validity of ZK proofs and the proper recording of nullifier hashes.

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Wallet Factory Test (test/WalletFactory.t.sol)

• Address Update:
  Changed mockWorldID to a hardcoded address.
• Test Update:
  Updated the test_CreateWallet function to use the new hardcoded mockWorldID address.

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Transfer Test (test/Transfer.t.sol)

• Mock Replacement:
  Removed the MockWorldIDContract and replaced it with MockWorldID.
• Proof Handling:
  • Updated tests to provide a valid ZK proof when calling the transfer function.
  • Added checks to verify both valid and invalid proofs.

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Mock World ID (test/mocks/MockWorldID.sol)

• Function Implementation:
  Implemented the verifyProof and generateZkProof functions to simulate ZK proof verification and generation.

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World ID Interface (src/IWorldID.sol)

• Interface Update:
  Updated the interface to include the verifyProof function, ensuring compatibility with the new ZK proof verification process.

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Summary

This PR improves the wallet contract by:

• Enhancing security with strict ZK proof verification.
• Optimizing contract behavior by using immutable variables and removing redundant code.
• Updating tests and interfaces to ensure consistency and correctness in handling ZK proofs and nullifier hashes.

Please review the changes and provide any feedback or suggestions for further improvement.

[mnusurov]

closes #1

[mnusurov]

hey @Dprof-in-tech friendly reminder )

[Dprof-in-tech]

This is beautiful work. Also I'm sorry for the time taken to review this. I've been away for a while